Ferrite beads are well known in the cabling industry, and are often used to shield sensitive data cables from extraneous electromagnetic noise and interference that may be present in the operating environment. A typical commercial ferrite bead may be available as a toroidal or donut shaped element sized to receive a cable. Ferrite beads may either be a solid, one-piece element or a split, two-piece assembly. The prior art is replete with devices and components designed to couple a ferrite bead to a cable. For example, a number of ferrite bead constructions and securing devices for ferrite beads are disclosed in the following patents: Meguro et al., U.S. Pat. No. 5,287,074, issued Feb. 15, 1994; May, U.S. Pat. No. 5,162,772, issued Nov. 10, 1992; and Cort, U.S. Pat. No. 4,818,957, issued Apr. 4, 1989. Although these and other prior art assemblies may adequately secure ferrite beads to cables, they may not be desirable to use in many practical applications.
The assembly disclosed by Meguro et al. includes a hinged shell that snaps around the ferrite bead to secure the ferrite bead to the cable. Such a construction is relatively expensive to manufacture and package, and the hinged portion of the shell may lack a sufficient amount of structural integrity. Furthermore, the ferrite bead or the shell may become lost during handling or installation because the ferrite bead is not attached to the shell. In addition, nothing prevents the ferrite bead from vibrating or rattling within the shell after it is installed upon the cable. Such movement of the ferrite bead may cause undesirable chafing of the cable insulation.
The prior art also includes ferrite bead assemblies that are intended to permanently affix the ferrite beads to the associated cables. For example, May discloses a device that snaps over the cable in a locking manner to prevent removal of the ferrite bead from the cable. As disclosed by May, the ferrite bead cannot be removed or adjusted without destroying the outer case that holds the ferrite bead. Thus, such prior art devices are limited to a single use and their lack of adjustability may add a significant amount to the cost of installing a large number of ferrite beads in, e.g., a complex communications system.
Cort discloses an alternate ferrite bead assembly that includes a resilient sleeve that slides onto the cable. After the sleeve is installed on the cable, the ferrite bead is pressed over the sleeve and maintained on the sleeve with two integral retaining ridges. The ferrite bead remains exposed after it is installed on the cable; the Cort device does not protect the ferrite bead from damage, nor does it protect the surrounding equipment and environment from damage caused by the ferrite bead.
Other prior art methods of securing ferrite beads to cables may also be undesirable for many applications. For example, a ferrite bead may be secured to a cable with shrink wrap tubing that covers the bead and a portion of the surrounding cable. Unfortunately, the shrink wrap material can be expensive, particularly when relatively thick ferrite beads are utilized (because the cost of shrink wrap tubing increases as the shrink-down ratio increases). For example, the material and labor cost to install a ferrite bead on a cable using a three inch section of high-shrink-ratio tubing can be $3.00 or more. In addition to its high cost, this procedure results in a relatively permanent installation. Consequently, removal or adjustment of the ferrite bead typically requires a good amount of labor and additional cost.
The use of over-molding or tie wraps to secure a ferrite bead to a cable may not be appropriate for the same reasons discussed above. For example, over-molding is a costly procedure that results in a relatively permanent installation of the ferrite bead. Removal requires additional labor to remove the bead and remold the bead in a new location upon the cable. The use of tie wraps, while relatively inexpensive and easy to install, also does not facilitate quick and easy adjustment and removal of the ferrite bead. In addition, the use of tie wraps merely secures the location of the bead on the cable; the cable is not protected from chafing by the bead and the bead remains exposed to the environment.
Accordingly, a ferrite bead assembly is needed that overcomes the above and other shortcomings of the prior art.